by Andrew Green
In the last NCMG column, Jenny Edwards wrote about the waratah anemone, a spectacular inhabitant of our rock pools. Of course there are many species of anemones to be found locally in the intertidal zone and below, and they all have at least one thing in common; as adults, they are fixed to the substrate - aren’t they? As Jenny said, anemones live a long time, so if you find a favourite anemone, you could mark the spot and come back to check or monitor its activity over a long period. An interesting project, perhaps?
But there is one species found locally which can move as an adult. Now there are crabs, sometimes called decorator crabs, which can physically remove anemones from their perches with their nippers, and ‘replant’ them on their shells. For protection perhaps? Or camouflage? Who knows – ask the crabs! That’s a story for another time. But I am not talking about such ‘involuntary’ movement – our ‘swimming’ anemone moves of its own accord.
You are more likely to find the swimming anemone (Phlyctenactis tuberculosa) if you snorkel or scuba dive, although I have seen it in large rock pools with plenty of water movement at low tide, where it may have been washed in. The best description I can think of is a fist-sized dollop of baked beans! It also comes in some rather attractive pastels, but baked beans seems the factory standard colour for these waters, albeit sometimes with lighter stripes. The analogy with beans is strengthened given that the surface of its column is packed with hollow, bean-like vesicles which are linked to its central body cavity.
When you do find one, its bright colour sticks out like the proverbial, against the olive brown kelp or crayweed it is often attached to. Its size is also characteristic – up to about 16 cm in height. During the day, it doesn’t look much like an anemone, until on close examination, you can see that the dollop is hollow, and there is an opening or mouth. It has drawn its crown of tentacles inside, rather like the waratah anemone does at low tide. But at night, it forms the typical tubular shape with the tentacles at one end, and a ‘foot’ at the other.
It can move either by crawling like a snail, for example to move higher up in the algal canopy to find a better feeding position, or by simply letting go, and tumbling with the currents until it decides (or is able) to re-attach itself. Strictly speaking, it doesn’t swim…
